1. Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly to wireless terminals that support multiple subscriptions using multiple transceivers.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. Examples of such networks may be based on the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). One example is the UMTS Terrestrial Radio Access Network (UTRAN), which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, including Time Division-Synchronous Code Division Multiple Access (TD-SCDMA), and code division multiple access (CDMA) or one of its variants such as Wideband-Code Division Multiple Access (W-CDMA). UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
Certain wireless networks identify subscribed users by means of a subscriber identity module (SIM). Some wireless devices support multiple concurrently installed SIMs and may provide a plurality of transceivers to support concurrent active connects. In one example, a dual active device (two transceivers) may support three or more SIMs and it is possible that two traffic calls (carrier-switched and/or packet-switched) can be active at the same time. For example, a tri-SIM device may maintain GSM+W-CDMA+W-CDMA, CDMA+W-CDMA+W-CDMA or another combination of connections. In another example, a quad-SIM device may maintain CDMA+W-CDMA+W-CDMA+GSM, W-CDMA+W-CDMA+GSM+GSM or another combination of connections.
If two SIMs are active on traffic calls in a dual-active device, the remaining SIMs generally enter an out-of-service (OOS) state. After ending the traffic calls, all SIMs will try to acquire a network and then enter an idle state on the acquired networks. The redundancy associated with this method can consume a substantial amount of power for acquisition of networks for multiple SIMs, and may require significant amounts of time to enter the idle state.